There are how many search engines!!

[There are]

I’m new to this forum as well as online industry. I have recently got a job in one of the SEO companies. I see so many activities happening in the office that I get confused. I don’t know what one service offers. So, I thought I will learn everything from the forum members. Can anyone inform me about different SEO services? How does SEO help a site on search engines? How many search engines are available on the World Wide Web? I am aware of Google, Yahoo and MSN. Are there any other Search Engines that I need to know?
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Seo Marketing|PPC